Speech gate



United States Patent O 3,532,834 SPEECH GATE Anthony J. Presti, Warren, NJ., assignor to Farrington Manufacturing Company, New York, N.Y., a corporation of Massachusetts Filed Sept. 20, 1968, Ser. No. 761,133 Int. Cl. Gl 1/02;G11b 27/36, 3.7/00

U.S. Cl. 179-1002 7 Claims ABSTRACT OF THE DISCLOSURE Disclosed is a speech gate for a sound spectrograph. Sound spectrographs monitor and/or analyze successive larger portions of a magnetic tape, each larger portion having recorded along the length thereof the sound to be analyzed, which typically is sensed by a scanning magnetic pickup head. The speech gate permits analysis of smaller portions within the above-mentioned larger portions of the tape. A delay counter is utilized to determine the beginning of the smaller portion and a gate counter, which is initiated by the output of the delay counter, is utilized to determine the length of this smaller portion. Connected to the above-mentioned scanner are a clock wheel and a start Wheel. The start wheel generates a pulse each time the scanner senses the beginning of the larger portion of the tape. This pulse permits pulses generated by the clock wheel to be gated to the delay counter, which generates its output pulse when a predetermined number of clock pulses have been generated. Since the clock and start wheels are connected to the scanner, the speech gate is effective regardless of the scanning speed.

BACKGROUND OF THE INVENTION This invention relates toa speech gate for use with a sound spectrograph.

The sound spectrograph is utilized to analyze the ampli tude and frequency content of sounds such as speech. The sound spectrograph has been described in various publications such as The Journal of the Acoustical Society of America, High-Speed Sound Spectrograph by Anthony I. Presti, vol. 40, No. 3, pp. 628-634, September 1966, and U.S. Pat. 3,355,551 granted to A. I. Prestigiacomo (name now changed to A. J. Presti) on Nov. 28, 1967. As is brought out in this prior art literature, the sound spectrograph typically analyzes a loop of tape approximately 2.4 inches long upon which is recorded speech or other acoustic information at the rate of 7.5 inches per second where a loop corresponds to one of a plurality of successive larger portions of the tape which are successively analyzed. The amplitude and frequency content of the recorded sound is determined by repetitively scanning the loop with a magnetic pick-up head. The scanner output modulates a carrier, the frequency of which is increased in synchronism with the successive scans of the loop. Also, the frequency is increased in accordance with the position of a stylus or the like in a recording device. The amplitude and frequency content of the sound thus produced is graphically portrayed on electrically sensitive facsimile paper which is marked by the stylus.

The above-described spectrograph provides a spectrum analysis of the entire 2.4 inch tape loop. However, there are instances where it is desired that only a portion of the 2.4 inch tape loop be analyzed. Heretofore, this capability has not been included in spectrographs.

That this capability would be desirable is evident from some of the applications to which spectrographs have been put or proposed. For instance, spectrographs have been employed to establish the identity of a particular 3,532,834. Patented Oct. 6, 1970 ICC person. Thus, if a persons voice were recorded beforehand, and if it were necessary to establish that a later recording of that persons voice was indeed a recording of his voice, then sound spectrograms could be made of each of the recordings and a comparison between the two would readily establish whether the later recording did indeed belong to the person in question. With the advent of legalized wire-tapping in certain restricted areas, it can be readily seen that this particular application will be of significant import.

Further, from the analysis of sound waves emitting from certain parts of the body such as the heart, medically diagnostic .tests can be performed with a high degree of accuracy. In order to provide a complete picture of the emitted sound, sound spectrographs are once again of significant importance.

SUMMARY OF THE INVENTION Thus, it is a primary object of this invention to provide a speech gate for use with a sound spectrograph.

It is a further object of this invention to provide within a sound spectrograph means for analyzing any selected portion of the tape loop presented for analysis.

Other objects and advantages of this invention will become apparent upon reading the appended claims in conjunction with the following detailed description and the attached drawing.

BRI'EF DESCRIPTION OF THE DRAWING The drawing isa schematic and block diagram of a sound spectrograph incorporating an illustrative embodiment of the speech gate in accordance with the invention.

DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT OF THE INVENTION Referring to the drawing there is shown a tape 10 upon which is recorded the sound kto be analyzed. As mentioned in the before mentioned prior art literature, the tape may be analyzed in successive 2.4 inch sections of the tape. As used in the claims and in the remainder of the specification, these larger 2.4 inch sections of tape correspond to rst selected portions of the tape. 'Referring to the drawing, one of the 2.4 inch sections of taper is shown at 12 looped around a drum generally indicated at 14. Disposed within the drum is a scanning assembly diagrammatically indicated at 16 which rotates within the drum and in intimate contact with the tape in the direction indicated. Thus, with each rotation of the scanning assembly, the tape loop 12 under analysis is scanned once. The output from scanner assembly 16 is applied to a scanner amplifier 18 and thence to gate 20. If the gate 20 is conditioned, the scanner output signal is then applied to analyzer 22, which converts the signal to a form suitable for use with marking drum 24, the analyzer signal being applied to drum 24 through marking amplifier 26. The analyzer 22 also performs the function of selecting a different frequency of the scanned signal with each successive scan of the tape 12 by scanner assembly 16. This is described in detail in the before-mentioned prior art literature.

The output of gate 20 is also to monitor amplifier 28 and thence to loudspeaker 30. As brought out in the 1before-mentioned literature, the scanner 16 can operate at either 7.5 inches per second or inches per second depending on the function which the spectrograph is to perform. Hence, when analyzing, it is desirable to operate at the higher speed and thus shorten the analysis time. However, when it is desired to monitor or hear the sounds recorded on the tape the scanning assembly 16 rotates at the same speed which was employed when the sounds were originally recorded on tape 10-that is, 7.5 inches per second. It is when this latter mode of operation is 3 employed, that the monitor amplifier 28 and loudspeaker 30 are employed. Also in this latter mode of operation the sound may be re-recorded on recorder 32 for further analysis. The analyzer 22, marking drum 24, loudspeaker 30, and recorder 32 are generically referred to as sound processing means in the claims.

In order that selected portions of the tape loop 12 may be analyzed or monitored, clock wheel 34 and start wheel 36 are provided. These selected portions will 'be referred to as second selected portions of the tape in the claims. The clock wheel 34 and start wheel 36 are mounted on or connected by appropriate gearing to the shaft which drives scanner assembly 16 and preferably they rotate in synchronism with the scanner assembly 16'. Clock wheel 34 produces a train of clock pulses while start wheel 36 produces a single start pulse for each revolution of the scanner assembly 16, the timing of the start pulse coinciding with the beginning of each scan of the tape loop 12. As indicated at 38 on start wheel 36 appropriate means for generating the start pulse are provided, Many means for generating such pulses are well known in the prior art. Typically, appropriate contact closing means can be secured on the periphery of the start wheel 36 to momentarily close a pair of contacts and thereby generate an electrical pulse. Disposed around the periphery of clock wheel 36 are a plurality of such pulse generating means and thus the train of clock pulses is generated whenever the scanner assembly 16 is scanning the loop 12.

The clock pulses are applied to gate `38 and thence to delay counter 40, which generates a delay pulse in a well known manner after a predetermined number of clock pulses have been counted. This predetermined number may be varied also in a well known manner to adjust the timing of the delay pulse. This pulse sets flip-flop 42 which in turn controls gate 20. Thus, when flip-flop 42 is set,

gate 20 is conditioned to pass the output of scanner 16 to analyzer 22 or monitor amplifier 28. The set output from flip-flop 42 is also applied to gate 43. Also applied to this gate are the clock pulses from gate 38. Gate counter 44 counts the clock pulses and when an adjustable, predetermined number have been counted an end-of-gate pulse is generated which is applied to the reset terminal of iiip-fiop 42 to thereby decondition gates 20 and 43.

The gate 38 is conditioned by a flip-flop 46, which in turn is set by the start pulse generated by start wheel 36. Since the start pulse occurs at the beginning of the scanning of tape loop 22, counter 40 commences counting the clock pulses at the beginning of each scanning interval. The output from counter 44 is also applied to the reset terminal of flip-flop 46. Thus, the speech gate feature of this invention will be deconditioned upon the occurrence of the pulse at the output of counter 44. Of course, with the next start pulse the above-described sequence of events recommences.

As stated before, the clock wheel 34 and the start wheel 36 preferably rotate in synchronism with the rotation of the scanner assembly 16. Hence, regardless of the speed of rotation of the scanner, the position of the speech gate and the width thereof can be respectively adjusted by merely adjusting the counts at which the counters 40 and 44 will generate an output pulse. Hence, the leading edge of the gate signal for gate 20 is determined by counter 40 while the width of this gate signal is determined by counter 44. Of course, if one desires to monitor or analyze the entire tape loop 12, all that is necessary is to set the delay counter 40 to a minimum and the gate counter 44 to a maximum. This will insure that the gate 20 is conditioned for the entire scanning interval.

Numerous modifications of the invention will become apparent to one of ordinary skill in the art upon reading the foregoing disclosure. During such a reading it will be evident that this invention provides a unique speech gate for accomplishing the objects and advantages herein stated. Still other objects and advantages and even further modifications will become apparent from this disclosure. It is to be understood, however, that the foregoing disclosure is to be considered exemplary and not limitative, the scope of the invention lbeing defined by the following claims.

What is claimed is:

1. In a spectograph including scanning means for repetitively scanning a rst portion of a tape upon which are recorded acoustic signals such as sounds and means for processing the sounds detected Iby said scanning means, a speech gate for analyzing a second selected portion of the tape, Within said first portion of the tape, said speech gate comprising:

first gating means connected between said scanning means and said sound processing means;

means responsive to said scanning means for generating a start pulse at the beginning of each scan of said first tape loop portion;

means responsive tosaid start pulse for generating a first pulse delayed a first adjustable predetermined amount of time with respect to said start pulse at the beginning of said second selected portion of the tape;

means responsive to said rst pulse for producing a second pulse delayed a 'second adjustable, predetermined amount of time with respect to said first pulse at the end of said second selected portion of the tape; and

said first gating means being responsive to said first and second pulses for gating the output signal from said scanning means to said sound processing means during the interval of time between said first and' second pulses.

2. A speech gate as in claim l1 where said means for generating said first pulse includes:

a clock pulse source responsive to said scanning means, the rate of the clock pulses being a function of the rate of relative movement between said first portion of the tape and said scanning means; and

first counting means responsive to said start pulse and said clock pulses for counting a predetermined number of said clock pulses after the occurrence of each of `said start pulses to thereby establish said first adjustable, predetermined amount of time.

3. A speech gate as in claim 2 where said means for generating said first pulse includes:

first bistable means responsive to said start pulse for being set to one of its two states; and

second gating means responsive to said first bistable means for passing said clock pulses to said first counting means when said first bistable means is set to said one state.

4. A speech gate as in claim 2 where said means for generating said second pulse includes:

second counting means responsive to said first pulse and said clock pulses for counting a predetermined number of said clock pulses to thereby establish said second adjustable predetermined amount of time.

5. A speech gate as in claim 4 where said means for generating said second pulse includes:

second bistable means responsive to said first pulse for being set to one of its two states; and

third gating means responsive to said second bistable means for passing said clock pulses to said second counting means when said second bistable means is set to said one state.

'6. A speech gate as in claim 5 where said first gating means is responsive to said second bistable means for gating said scanning means output signal to said sound processing means when said second bistable means is set to said one state;

said second bistable means is responsive to said second pulse to be reset to the second of its two states to thereby disconnect said scanning means from said sound processing means; and

said first bistable means is responsive to said second pulse to be reset to the second of its two states to thereby disconnect said clock pulse source from said rst counting means.

7. In a spectrograph including scanning means for repetitively scanning a first portion of a tape upon which are recorded acoustic signals such as sounds and means for processing the sounds detected by said scanning means, a speech gate for analyzing a second selected portion of the tape, within said first portion of the tape, said speech gate comprising:

a clock pulse source responsive to said scanning means, the rate of the clock pulses being a function of the rate of relative movement between said first portion of the tape and said scanning means;

means responsive so said scanning means for generating a start pulse at the beginning of each scan of said first tape portion by said scanning means;

first counting means responsive to said clock pulse source and said start pulse generating means for counting said pulses and for generating a first pulse at the beginning of said second selected portion;

second counting means responsive to said clock pulse source and said first counting means for generating a second pulse at the end of said second selected tape portion;

gating means for connecting said scanning means to said sound processing means; and

means for conditioning said gating means responsive to said first and second pulses for establishing the speech gate interval.

References Cited UNITED STATES PATENTS 2,611,828 9/1952 Gunby 179-1002 3,317,680 5/1967 Porter 179-1002 3,355,551 11/1967 Prestigiacomo 179--1002 BERNARD KONICK, Primary Examiner R. S. TUPPER, Assistant Examiner U.S. C1. X.R. 

